Two beta -hydroxyphosphonate analogs of M6P have been prepared by condensat
ion of the lithiated anion of methyldiethylphosphonate with the C-6 carbony
l of a mannose derivative. The diastereoisomers thus obtained have been sep
arated and the absolute configuration at the B-position has been determined
by spectroscopic analysis in conjunction with theoretical calculations. Re
cognition phenomena by M6P/IGFIIR have been evaluated for both diastereoiso
mers.